<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>阶乘</title>
</head>

<body>
    <script>
    function factorialize(num) {
        if (num === 0) { return 1; }
        return num * factorialize(num - 1);
    }

    factorialize(5);

    factorialize(5);
    </script>
</body>

</html>